Conventional alkylene oxide block copolymers include, for example, HO--C.sub.2 H.sub.4 O).sub.a (C.sub.3 H.sub.6 O).sub.b (C.sub.2 H.sub.4 O).sub.a H (a=2 to 70, b=10 to 50), formed by block copolymerization of a water-insoluble polypropylene glycol and ethylene oxide, and HO--C.sub.3 H.sub.6 O).sub.a (C.sub.2 H.sub.4 O).sub.b (C.sub.3 H.sub.6 O).sub.a H (a=2 to 70, b=10 to 50), formed by block copolymerization of polyethylene glycol and propylene oxide as described in Chemistry Express, Vol. 1, No. 10, pp. 615 to 618 (1986). These block copolymers are nonionic polymeric surfactants containing a variety of combinations of hydrophilic alkylene oxide segments (the term "segment" as used herein unless otherwise indicated refers to an alkylene oxide segment) and hydrophobic segments.
In addition, various multiblock segment polyurethanes have been synthesized, containing polyether compound segments such as polyethylene oxides, polypropylene oxides, polytetramethylene oxides, etc., as soft blocks and segments that are the reaction product of a short chain diol or diamine and a diisocyanate as hard blocks. The physical properties of these polyurethanes are being investigated in detail to permit their use as fiber materials or elastomer materials. In this case, the kinds of soft segments and hard segments, and their relative proportions, as well as the crystallinity and morphology of the polymers resulting from the intermolecular force between the individual segments therein are mainly studied from the viewpoint of the mechanical and physiological characteristics of the polymers.
In general, the chemical structure of surfactants necessarily includes a hydrophilic group and a lipophilic group in one surfactant molecule, and such surfactants are called amphiphilic substances. In particular, these include polymers which can form stable colloidal particles like micelles of low molecular surfactants, when dissolved in a liquid, which may be a solvent either for the hydrophilic segment or the hydrophobic segment. Such polymers are currently being studied. Block copolymers having both hydrophilic segments and hydrophobic segments (along with graft copolymers having both segments) are called amphiphilic polymers.
In block copolymers, the characteristics of each segment, and in particular, its hydrophilicity or hydrophobicity, are important, and are determined by the hydrogen bond, Van der Waals force or ionic bond between each segment of the copolymer and a low molecular compound, ion, water, metal, etc., as well as the physicochemical characteristics of the molecular aggregate composed of the polymer and the low molecular compound (including, for example, the hydrophilicity-hydrophobicity interaction between the polymer and water or a solvent, the influence of ions on the stereostructure and phase separation of the polymer, the interaction between the polymer and a surfactant appearing in the cluster formation therebetween, etc.). Unlike known copolymers as described, for example, in Polymers Preprints Japan, Vol. No. 35, No. 7, the amphiphilic block copolymers of the present invention contain segments chosen to permit specific interactions between the polymer and a low molecular compound, especially in consideration of the degree of the hydrophilicity or the hydrophobicity of the segments.
However, since segment polyurethanes are block copolymers which have a structure made up of a combination of plural segments bonded by the urethane bond, these have many useful characteristics (such as viscoelasticity, etc.) which are not found in other block copolymers having a structure composed of directly bonded segments. These characteristics, in combination with the effective utilization of the hydrophilicity or hydrophobicity of each segment, permit various additional applications of segment polyurethanes besides their use as polymeric surfactants.